Recently, various technologies for improving radio communication quality have been developed. For example, radio communication devices that implement carrier reproduction by eliminating phase noise components from carrier phase signals detected from baseband signals have been developed.
FIG. 4 is a block diagram showing a radio communication device having a carrier phase noise elimination function. Herein, radio communication is conducted between a first radio communication device 300 and a second radio communication device 400.
In the first radio communication device 300, an antenna 24 receives a radio signal transmitted by the second radio communication device 400 so as to send it to a reception part 25. Additionally, the antenna 24 transmits a transmission signal, input by a transmission part 30, to the second radio communication device 400.
The reception part 25 of the first radio communication device 300 converts a reception signal of the antenna 24 into a baseband signal, implements clock synchronization and carrier synchronization, and then sends it to a demodulation part 28 and a carrier reproduction part 26.
The carrier reproduction part 26 of the first radio communication device 300 detects a carrier phase signal from a baseband signal so as to send it to a carrier reproduction filter 27. The carrier reproduction part 26 implements carrier reproduction using a carrier phase signal from which its noise component is eliminated by the carrier reproduction filter 27. The carrier reproduction part 26 sends the reproduced carrier signal to the reception part 25, which thus implements carrier synchronization on a baseband signal.
According to a filtering characteristic which has been determined in conformity with a phase noise characteristic presumed in a design stage, the carrier reproduction filter 27 of the first radio communication device 300 eliminates a noise component from a carrier phase signal input by the carrier reproduction part 26. The carrier reproduction filter 27 sends back the carrier phase signal, from which its noise component has been eliminated, to the carrier reproduction part 26.
A demodulation part 28 of the first radio communication device 300 receives and demodulates a baseband signal of the reception part 25, thus sending a demodulated radio frame to an external device. On the other hand, the modulation part 29 modulates a radio frame input from the external device so as to send a baseband signal to the transmission part 30. The transmission part 30 converts the baseband signal of the modulation part 29 into a radio frequency signal (an RF signal), thus sending it to the antenna 24.
The second radio communication device 400 includes a modulation part 21, a transmission part 22, an antenna 23, a reception part 31, a carrier reproduction part 32, a carrier reproduction filter 33, and a demodulation part 34, thus carrying out the same radio communication process as the first radio communication device 300.
Patent Document 1 discloses a phase synchronization circuit having a phase noise detection function that compares a reception signal and a reference signal so as to detect phase noise in a radio communication device.